1. Field of the Invention
The present invention relates to an electrical rotating machine usable as a vehicle generator motor for use in an energy-saving automobile such as an idling stop vehicle, and more particularly to an electrical rotating machine having integrated therewith a switching circuit section for controlling a current supplied to a stator winding.
2. Description of the Background
As a general electrical rotating machine for use in a vehicle, a separate type in which an inverter for controlling the electrical rotating machine is mounted in a vehicle separately from the electrical rotating machine has been actually used. In the case of the separate type, a space for accommodating the inverter needs to be secured in a vehicle. In addition, a loss is caused by the length of a harness connecting the electrical rotating machine and the inverter. In order to solve these disadvantages, various types of inverter-integrated electrical rotating machines have been developed.
As a conventional machine, there has been an electrical rotating machine having a power element unit integrated therewith or arranged in the vicinity thereof, in which a plurality of power elements (switching elements) constituting a power element unit, and an inner heat sink and an outer heat sink, which are connected to the power elements, are arranged in a space between a cover arranged on the rear side of a rear bracket and the rear bracket, in a manner to be fixed on an outside surface of the rear bracket via supporting members (see particularly FIG. 1 of Japanese Laid-Open Patent Publication No. 2006-211835, hereinafter referred to as Patent Document 1).
Since the conventional electrical rotating machine is structured as described above, a path of heat, which is generated from the stator winding, passing through a housing that forms a contour, and reaches an inverter circuit, is short. Accordingly, the inverter circuit suffers the heat from the stator winding, and a temperature thereof is increased higher than the specification thereof. The electrical rotating machine thus attempts to meet the specification temperature, resulting in insufficient output performance. Further, since a power circuit unit and a brush holder are arranged outside the rear bracket, a length of the rear bracket in an axial direction is short, and consequently a heat transmission path becomes short. Accordingly, an effect of the heat has been significant.
Further, the surface of the switching elements, the surface having an electrical potential, is directly joined onto the heat sink by soldering or the like, and thus the heat sink also has the electrical potential. Accordingly, when the heat sink is fastened to the housing or the like with screws, an insulating material needs to be interposed therebetween before fastening. The insulating material tends to deteriorate over time, which leads to deterioration in fastening power, and leads to component damage which is accelerated by vibration of a vehicle body.
Further, when the heat sink has an electrical potential, in order to secure safety against collision, a sufficient spatial distance needs to be arranged between a material having no electrical potential such as the housing, and the heat sink, which leads to a problem of upsizing of the entire machine. In order to avoid such upsizing, insulating coating may be applied to the heat sink. However, the insulating coating is expensive, and, in addition, will be deteriorated by salt water. That is, the insulating coating is insufficient from a viewpoint of reliability.